Flasher IC
Features
• Temperature and Supply Voltage Compensated Flashing Frequency • Frequency Doubling Indicates Lamp Outage • Re...
Description
Features
Temperature and Supply Voltage Compensated Flashing Frequency Frequency Doubling Indicates Lamp Outage Relay Driver Output with High Current Carrying Capacity and Low Saturation Voltage Minimum Lamp Load for Flasher Operation: ≥ 1W Very Low Susceptibility to EMI Protection According to ISO/TR 7637/1 Level 4
Flasher IC with 30-mΩ Shunt
1. Description
The bipolar integrated circuit U643B is used in relay-controlled automotive flashers where a high-level EMC is required.
Lamp outage is indicated by frequency doubling during hazard warning as well as direction mode.
U643B
Rev. 4727B–AUTO–09/05
2. Block Diagram
Figure 2-1. Car Flasher Application Circuit, Resistor R1 and R2: 0.25W; R4 for Protection Against Continuous Reversed Polarity: 0.5W
C1 4
6
Measuring comparator K 1 V 6-81 mV 20 kΩ
K1
2 5 kΩ
7
R3 Shunt
30 mΩ
+ VS + 49
K2 Pulse R1 generator
49 a-Comparator K 2 20 kΩ
49 a-Comparator K 3
K3 5
20 kΩ
3
Relay 8 R2
23 V 5 kΩ IC Ground
1
1.5...2.2 kΩ R4
470 Ω
49 a
5 W 21 W 21 W
21 W 21 W 5 W
GND - 31
Indicator lamps
2 U643B
4727B–AUTO–09/05
3. Pin Configuration
Figure 3-1. Pinning
GND 1
8 SI
VS 2 REL 3
U643B
7 LD 6 VS
OSC 4
5 OSC
Table 3-1. Pin 1 2 3 4 5 6 7 8
Pin Description
Symbol Function
GND
IC ground
VS Supply voltage VS REL Relay driver
OSC OSC VS LD
C1 Oscillator R1 Oscillator Supply voltage VS Lamp failure detection
SI Start input (49a)
U643B
4727B–AUTO–09/05
3
4. Functional Description
4.1 Pin 1, GND
The ...
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